Fastener device



Oct. 30, 1962 R. w. Hl-:NNING ETAL FASTENER DEVICE 2 Sheets-Sheet l Filed Dec. 6, 1955 FIGJ Oct. 30, 1962 R. w. HENNING ETAL 3,060,435

FASTENER DEVICE Filed Deo. s, 1955 2 sheets-sheet 2 nited States This invention relates to improvements in a fastener driving tool and more specifically to a tool of the explosive powder actuated type.

This invention relates to a type of tool having a barrel telescopically or reciprocatably carried in a housing which may be opened for convenient loading between a front housing portion which carries the barrel assembly and a rear housing portion which carries the actuating assembly at the breech of the tool. This type of tool for safety purposes also may have a safety shield together with control of the angle of lire. The shield is mounted slidably at the muzzle of the tool and is yieldably urged against the wonk surface. A specific example of such a tool is that described in copendin-g patent application Serial No. 355,034, tiled May 14, 1953, by Kopf et al., now Patent No. 2,945,236, issued July 19, 196Q. reklthough the tool of this invention is described herein with reference to the tool shown in the Kopf et al. application, it is to be understood that the invention may take various forms and may be applicable to other tools of the type contemplated herein. This invention, therefore, relates to explosive operated tools of any suitable type in which it makes for easy replacement of the barrel and facilitates the use of any one of a plurality of different barrels.

In explosive operated stud driving tools quick interchangeability of barrels of different calibers right on the job is desirable for the obvious reason that this conveniently permits various sizes of fasteners to be driven with the same tool as the changing needs of the fastener driving operation requires. For example, two barrels, one for driving 1A inch fasteners and the other for driving inch fasteners, will suffice for the bulk of the driving needs encountered on the ordinary job. With a tool having two readily interchangeable barrels of this caliber, one barrel can conveniently be carried by the operator in his pocket, for instance, while the other is in use. But changing of barrels in explosive actuated stud driving tools has heretofore been not `only rather inconvenient but also presented an clement of danger as well as the loss of driving power. In changing of the barrels there is always the possibility that the tool operator may .not completely install the barrel in the proper final position. A11 improperly installed barrel will not give the desired relationship between the power cartridge case at the breech and the firing mechanism of the tool. In fact improper installation of the interchangeable barrel may leave parts of the cartridge case sidewalls unsupported and subject to distention and even to bursting in the tool. Furthermore, in certain tools of the aforementioned type, unless the interchangeable barrel is seated fully, the safety feature of the tool which insures that the stud or fastener is driven in a direction substantially perpendicular to the work surface is greatly impaired and fasteners may then be driven obliquely with respect to the surface and ricochet. A still further disadvantage of heretofore available tools characterized by interchangeability of barrels has been the danger of the barrel working loose during use.

Therefore, an object of this invention is to provide a` tool with a readily interchangeable barrel without the disadvantages and danger of improper installation of the arent 3,0%,435 Patented oci. so, rss2 ice barrel. Still another object is the provision of a tool which automatically will not Ifire should the 'barrel be installed improperly and worlc loose, or if the barrel be incompletely installed. Other objects and advantages will become apparent from a description of a specific embodiment set forth hereinafter when read in connection with the accompanying drawing in which:

FIG. l is a partial cross sectional longitudinal view through the front part of a preferred embodiment of the tool of this invention with the rear or handle part pivotally separated from the front or barrel section;

FIG. 2 is a transverse cross sectional view taken on line 2 2 of FIGURE 1;

FIG. 3 is a cross sectional longitudinal view of the tool of FIGURE 1 with the ymuzzle of the barrel pressed against the work surface and with the tool housing or casing also thrust toward the surface, in which position the tool may be said to be in the ready-to-iire position;

FIG. 4 is a fragmentary longitudinal view in cross section with a suitable enlargement for better showing how operation of the tool is prevented when the barrel is improperly installed; and

FIG. 5 is a transverse cross sectional view comparable to FIGURE 2 but differing in showing a plurality of ball detents.

In general the object of this invention is accomplished by a novel arrangement, structure and combination of parts making it impossible to iire the power cartridge and thereby eject the fastener unless the barrel is fully seated. Each of the interchangeable barrels is designed so that when properly seated it will coact with a control member carried in the tool housing and more specifically in the barrel receiver `or collar to avoid interference with the reciprocation of the barrel receiver or carrier and the barrel in the housing which is necessary for tool operation. This member preferably takes the form of a detent such as one or lmore hard steel balls each seated in a radially extending hole in the barrel receiver. The ball is mounted so as to be held captive in the hole but moveable therein so as to be capable `of extending either beyond the outer surface of the receiver or beyond the inner surface of the receiver which surrounds a portion of the barrel. For cooperation with this control member, the barrel is provided with a circumferentially extending groove so disposed lengthwise of the barrel as to align the groove in the barrel with the hole and ball in the receiver when the interchangeable barrel is substantially fully seated in the receiver. In this position the ball can protrude into the groove and forms no outer extension beyond the outer surface of the receiver. However, when the barrel is improperly installed in the tool the barrel is forced to protrude from the outer surface of the receiver, thereby forming an extension which interferes with movement of parts of the tool necessary to put the tool in the ready-to-fire condition. Two balls diametrically opposite each other or three balls sub stantially equally spaced around the circumference of the barrel may be employed particularly when liberal tolerances are used in manufacturing the tool.

Furthermore, it is preferred ythat a portion of the barrel surface is tapered so as to mate with a corresponding tapered surface on the barrel carrier. For example, a male tapered surface on the barrel is provided to fit snuggly with a female tapered surface in the carrier so as to better resist any tendency of the barrel to work loose during use.

It is also contemplated according to this invention that each barrel be capable of being readily removed or installed from an open end of the tool housing, preferably the muzzle end. Axial insertion followed by a few twists is all that is necessary to seat the barrel; and the reverse to unseat it for removal. Any quick but positive means of securing the barrel in the barrel receiver is provided, preferably screw threads.

The tool as shown in the figures of the drawing consists of a pistol grip or other suitable handle 20 at the rear carried fast on a rear housing 30, an interchangeable barrel 22 `and barrel carrier or receiver 100 assembled therewith to form a barrel assembly housed largely in an outer front housing tube 54 which in turn is carried on the tube collar 51 connectable with the rear housing 30. Tube collar 51 engages threadedly with the interior of the outer front housing tube 54. Extending from the rear end of collar 51 and integral therewith is a bayonet type of connection of the type consisting of circumferentially spaced lugs Slb extending for example, radially outwardly so as to be adaptable for engagement with a corresponding set of lugs 63 (FIGURE 3) spaced circumferentially and extending radially inwardly as a part of the front portion of the firing mechanism or rear housing 30. The barrel receiver or carrier is a collar 100` connectable with a breech lock 37 which is carried in housing 30 and is provided in turn with a tiring pin orifice 37a through which the tip of pin 34 may project. Breech lock 37 is provided with an interrupted female thread 37t for releasable engagement with a male interrupted thread 100i formed about the breech of barrel receiver 100. This arrangement provides a closure admitting of easy opening and closing with respect to the breech of the barrel at which an explosive power cartridge 23a is seated for driving the fastener 23b for ejection `from the muzzle of the barrel 22.

In order to adapt the tool for interchangeability of barrels of different configuration particularly in the calibers needed for the various sizes of fasteners or studs to be driven, the barrel portion of this tool is made of two parts, namely the barrel collar or receiver 100 and the interchangeable barrel 22. This barrel 22, like a regular permanent barrel, is of full length without the intermediate joints of ra longitudinally segmented barrel, but at the rear end it is of reduced outer diameter so as to be receivable in barrel collar 100. This portion of reduced diameter is preferably tapered at 114 so as to adapt `the barrel to tit tightly with the corresponding collar taper 115 Iand substantially resist any tendency of the barrel to work loose. Receiver 100 is mounted slidably in collar 51 so as to permit relative limited longitudinal reciprocating movement between receiver 100 and the front housing or outer tube collar 51 as permitted by the extension of stop pin 53 reciprocatably in lthe longitudinal slot 101 of barrel collar 100 when the tool is not firmly pressed against the work. Such relative movement occurs when the tool is thrust against the work surface 25 causing the coupled two-part housing and collar 51 to move as a unit with respect to the receiver or collar 100 in assembly with the barrel 22 in stationary abutment with respect to the work surface. Movement may also occur when the tool is not aligned squarely to the work piece in which event the barrel 22 and collar 100 in assembly move forward with respect to the housing for the particular kind of tool here disclosed. Bar-rel 22 is constructed so as to be readily secured within collar 100 by any suitable quick-connect means such as and preferably by male screw threads 102 engaging with the corresponding female threads 103 of receiver 100. To facilitate installation and removal of the barrel, it has two oppositely disposed flats 104 at the muzzle by which it may be engaged by a socket or Spanner Wrench and turned.

At this reduced rear end with particular reference to FIGURE 4, barrel 22 has a circumferential groove 105 alignable axially with a radial hole 106 in collar 100. This hole serves as a seat for aball 107 movably mounted vin hole 106 but retained therein by the inwardly projecting rims 108 (FIGURE 4) which do permit ball 107 to protrude either from the inner end of hole 106 into groove 105 or to protrude from ythe outer end of hole 106. The relationship of vthe ball diameter and wall thickness of collar 100 is such that unless ball 107 extends into groove 105, it will be forced to protrude from the outer end of hole 106 in which position the extending ball interferes with the front face of housing collar 51 and prevents placement of the tool into the ready-to-re position. Thus the tool is rendered inoperative unless the barrel is placed in collar 100 properly, in which position ball 107 forms no interference with collar 51. The split ring members and the release ring 82 in the operative position shown in FIGURES 1 and 3 and in greater detail in the enlargement of FIGURE 4 have suffcient clearance with receiver so as to provide no interference to the ball 107.

When mounted in the collar 51, the barrel and barrel collar 100 form an assembly slidably mounted with respect to housing tube collar 51 which forms an abutment indirectly for one end of the safety shield or barrel spring 26 the other end of which is in abutment with the safety shield assembly consisting of the safety tube 70 and an outwardly extending hollow shield 24. Although safety shield spring 26 does not abut directly with collar 51 it acts directly upon a barrel lock release ring 82 which in turn acts upon a pair of C-shaped gripper members 80, arranged in the form of an interrupted or split annulus which serves as a barrel lock or latch under the impetus of an annular split spring 81 biasing members 80 inwardly to engage in the inclined circumferential groove 109 on the periphery of the barrel receiver 100. As set forth in the aforementioned Serial No. 355,034, members 80 have a conical female surface which coacts with the corresponding male surface of the barrel lock release S2. Thus this release when acted upon by spring 26 keeps the members 80 out of groove 109 and allows the housing to move relative to the barrel assembly to the ready-to-re position so long as the tool has its shield 24, carried on tube 70, which under the action of compression spring 26 is kept biased to extend forwardly with respect to the front housing 54 and toward the muzzle plane 150 of the tool which is perpendicular to the axis of the bore of the tool barrel. The telescoping shield assembly is prevented from moving ahead of the barrel muzzle by means of a retainer nut or cap 75 screwed on to the barrel muzzle and of slightly larger outside diameter than the barrel muzzle.

The handle or grip 20 is mounted over the cup shaped rear housing 30 the front portion of which includes connection means which protrude forwardly from the handle 20. As shown more clearly in FIGURE 5 of aforementioned Serial No. 355,034, mounted for rotatable movement through a limited circumferentially extending arc with respect to rear housing 30 and acting through register pin 59 extending into a corresponding slot adjacent the front end of housing 30 is a mounting ring 58 having a pair of slotted ears, which in turn are adapted to pivot about a transverse connecting pin 61 and also to have limited longitudinal motion with respect to pin 61 mounted fast to the front housing tube 54 and its outer tube collar 51. This slotted hinge hole and bayonet coupling arrangement permits rear housing and its assembly of parts to be separable within limits of the coupling as a single unit from the front housing and its assembled members. This unit includes the cup shaped breech lock 37, cocking pin 40 carried on the breech lock 37, the spring biased firing pin 34, its biasing spring 35, the tiring pin pawl 42, the pawl spring 43, the trigger 46 and also the breech lock return spring 38.

At the breech of the barrel 22 there may be provided a detachable breech plug 56 insertable into the barrel for loading and removable from the barrel for the purpose of extracting the cartridge case 23a when spent. The bore of plug 56 is adapted to receive the cartridge cases 23a as shown in FIGURE 3.

In order to remove a barrel, starting from the position of the parts as shown in FIGURE l, the operator first presses the safety shield assembly including the shield 2.4 back against the front portion of the housing tube 54 which leaves the front end of the barrel fully exposed. In this position, retainer nut 75 is exposed so that it can be unscrewed. Then while holding shield 24 retracted, the operator applies a wrench or the like to the ilats 104 at the muzzle of the barrel and applies torque until the barrel Z2 turns freely and may be removed.

Another barrel of desired caliber is then inserted and screw threadedly engaged at its threads 102 with collar 0. The operator applies torque at the ats 104 until threads 102 are tightly engaged with the female threads 103 of the carrier or barrel collar 100 in which position the tapered part 114 of the barrel is tightly wedged into the `complementa-ry `female taper 115 of the collar 100. Finally the operator replaces the retainer nut 75 at the muzzle of the newly installed barrel 22. Thus, it is apparent that installation and replacement of the barrel in the tool of this invention can be very quickly and conveniently accomplished.

The taper lock shown is one of about 10 formed between the threads and the shoulder at which the outer diameter of the barrel is reduced and abuts with the carrier. However, the entire reduced rear portion of the barrel back of the threads may be provided with a slight taper for the sarne purpose. In this event, the taper is so slight that even when the barrel is installed partially, the ball 107 still protrudes with interference.

As shown in FIG. 5, there may be advantageously provided a modified barrel collar 200 carrying ball 207 and ball 307 uniformly spaced from each other for coaction with the groove 105.

In operation, the tool is first loaded in the position assumed when the halves of the tool are separated pivotally as shown in FIGURE l. With the projectable fastener 23h and the cartridge 23a emplaced in the barrel, the breech receiver assembly is swung, pushed and turned into engagement with the barrel receiver assembly as shown in FIGURE 3. Preparatory to firing the tool is then put into the ready-to-fire position shown in FIGURE l where the muzzle of the barrel is thrust into abutment with the work surface 25 while the tool casing, including the front and rear receivers, is telescoped forwardly or in the direction of the muzzle plane 150 of the tool and of the barrel, thereby placing the initiating parts of the tool into the relationship shown in FIGURE 3. In this position, assuming the barrel 22 is properly installed, the barrel and its collar 100 are retracted relative to the tool housing or casing, which is to say the casing is disposed forwardly with respect to the barrel as it is pressed against the work. The tool operator in order to tire the tool then need only pull the trigger 46 so as to release the firing pin 34.

Upon completion of the driving operation, the operator need then merely release the thrust upon the tool and by suitable rotation of the handle 20 through an angle of about 45 followed by a longitudinal rearward pull put the barrel receiver assembly and the rear receiver assembly in position for pivotal separa-tion as shown in FIG- URE 1.

This invention secures various advantages. In the first place the one piece full length barrel avoids the loss in power which occur as a result of explosive gas leakage in tools having a barrel assembly which consist of longitudinal segments attached to each other leaving joints along the effective length of the barrel. Another advantage is the assurance that the safety feature of the tool which prevents firing unless the barrel is square with the work is in operation. For such operation the barrel must be fully turned down. An insufficiently installed barrel is in effect an overly long barrel. Upon thrusting of the tool against the work such a barrel would either cause the angle of iire control feature of the tool to become effective only at excessive variations from the desired perpendicular or may even force the tool to fire only at an undesirably large oblique angle. Still another advantage is that the operator is not subject to the danger of a bursting cartridge in a tool of the type having no breech plug 56. Whether or not the tool has a breech plug, this invention prevents the loss of power which will occur at the breech of the barrel unless the barrel is in place all the way. A still further advantage is that the arrangement of this tool is not only very sensitive to variations in position of the barrel so as to render the tool inoperative unless each barrel is substantially fully installed but also is quite effective in maintaining the barrel in proper position while 1n use.

While a preferred embodiment has been described in the foregoing, it is to be understood that various changes in details and modifications may be made by those skilled in the art without departing from the spirit and scope of this invention as set forth in the appended claims.

What is claimed is:

'l. An explosive actuated tool for driving a stud, pin, or the like fastener into a work surface comprising a tool housing with an elongated front portion and a handle rear portion, a safety shield with a work engaging periphery disposed substantially perpendicular to the axis of said tool, said shield being mounted on the tool for axial movement of the housing with respect to said shield from a rearward normal position to a forward fully displaced position in abutment with said shield at lwhich said shield periphery is in the muzzle plane of said tool, a tiring pin within said housing, means for cocking said firing pin as said housing is moved forward relative to said muzzle plane as said handle portion is thrust forwardly, a barrel carrier slidably mounted within said housing and having a cylindrical passage therethrough, and a readily installed and replaceable forwardly extending barrel a portion of which engages with positive axial constraint with said carrier so as to seat the breech end of said barrel in said barrel carrier with positive axial engagement and projecting from said housing to said muzzle plane which is perpendicular to the axis of the bore of said barrel, and safety means in said carrier interposed between said housing and barrel, said safety means being inoperative only when said barrel is fully seated in said carrier to prevent movement of said housing relative to said muzzle plane and to said barrel and barrel carrier assembly from a normal extended safety position to a forward fully displaced ready-toere position, but operable to prevent movement to the ready-to-re position when said barrel is not so seated, said positive axial constraint with engagement occurring at said passage and a mating reduction of the barrel at said end between rearwardly converging tapered shoulders on said barrel and carrier and between threads of a connection on part of said passage and reduction intermediate said shoulders and a terminal Unthreaded part of said passage and reduction.

2. An explosive actuated tool for driving fasteners comprising one of a series of readily detachable and replaceable interchangeable barrels each with a diierent caliber of bore for ejecting a fastener into a work surface and each of substantially full barrel bore length adapted to carry an explosive power cartridge at the breech, a carrier with a through passage for seating over the whole carrier in open breech relationship one of said barrels in normally axially fixed assembly, a housing slidably carrying said carrier and having also a breech closure and a firing pin resiliently biased to spring toward the breech of said barrel to ignite said cartridge, safety shield means mounted reciprocably about the muzzle end of said barrel, means mounted on said barrel for retaining said safety shield means with respect to the barrel with constraint against movement ahead of said muzzle end of the barrel, said barrel and carrier having means for attaching both in axial assembly and being mounted for axial movement of said housing relative to said assembly between a normal extended safety position of said tool and a contracted ready-to-re position of said tool with said barrel and tiring pin in said respective positions being remotely spaced apart and spaced in close proximity adjacent each other respectively, said safety shield means being adapted for movement normally between said housing and retaining means and being in abutment with at least the latter of said retaining means and said housing in said ready-to-iire position of said barrel and carrier assembly, said firing pin adapted to be put in the cocked position when said barrel and carrier assembly are in the ready-to-re position in which position said ring pin may effectuate operation of the tool, and means mounted on said carrier for operative alternate abutment with said housing and barrel for preventing movement of the housing with respect to said barrel and carrier assembly to the ready-to-iire position by abutment with said housing unless said ybarrel is fully assembled with and seated in said barrel carrier whereat said means is in abutment with said barrel.

3. An explosive actuated tool for driving fasteners comprising one of a series of readily detachable and replaceable interchangeable barrels each with a different caliber of bore for ejecting a fastener into a work surface and adapted to carry an explosive power cartridge at the breech, a carrier for seating and carrying said one of said barrels, a housing slidably carrying said barrel and barrel carrier and having a tiring pin resiliently biased to spring toward the breech of said barrel to ignite said cartridge, safety shield means mounted reciprocably about the muzzle end of said barrel, means for retaining said safety shield means at said muzzle end of the barrel, said barrel and carrier both in assembly being mounted for axial movement of said housing relative to said assembly between a normal extended safety position of said tool and a contracted ready-to-fre position of said tool with said barrel and ring pin in said respective positions being remotely spaced apart and spaced in close proximity adjacent each other respectively, said safety shield means being adapted for abutment with said housing in said ready-to-iire position of said barrel and carrier assembly, said tiring pin adapted to be put in the cocked position when said barrel and carrier assembly are in the readyto-iire position in which position said ring pin may effectuate operation of the tool, and means for preventing movement of said barrel and carrier assembly to the ready-to-fre position unless said barrel is substantially fully and properly seated in said barrel carrier, said barrel and barrel carrier engaging screw threadedly, and said means for preventing movement of the housing with respect to the barrel and carrier assembly including a captive ball movably and protrudably carried in a radial slot in the barrel carrier and a circumferentially extending groove in the barrel alignable with said ball protrusion when said barrel is substantially fully assembled with said carrier.

4. The tool of claim 3 including a male conical portion on the barrel engageable with a corresponding female conical portion in the carrier to provide a locking taper lit between the barrel and carrier.

5. An explosive actuated tool for driving fasteners comprising one of a series of readily detachable and replaceable interchangeable barrels each with a different caliber of bore for ejecting a fastener into a work surface and each of substantially full barrel bore length adapted to carry an explosive power cartridge at the breech, a carrier for seating and carrying said one of said barrels in normally open breech flush relationship and axially xed assembly, a housing slidably carrying said carrier and having a breech closure and a tiring pin resiliently biased to spring toward the breech of said barrel to ignite said cartridge, safety shield means mounted reciprocably about the muzzle end of said barrel, means mounted on said barrel for retaining said safety shield means with respect to the barrel with constraint against movement ahead of said muzzle end of the barrel, said barrel and carrier having means for attaching both in axial assembly and being mounted for axial movement of said housing relative to said assembly between a normal extended safety position of said tool and a contracted ready-toire position of said tool with said barrel and firing pin in said respective positions being remotely spaced apart and spaced in close proximity adjacent each other respectively, said safety shield means being adapted for movement normally between said housing and retaining means and being in abutment with at least the latter of said retaining means and said housing in said ready-toiire position of said barrel and carrier assembly, said firing pin adapted to be put in the cocked position when said barrel and carrier assembly are in the ready-to-fire position in which position said tiring pin may effectuate operation of the tool, and means mounted on said carrier for operative alternate abutment with said housing and barrel for preventing movement of said barrel and carrier assembly to the ready-to-fire position by abutment with said housing unless said barrel is fully and properly seated in said barrel carrier whereat said means is adapted for movement interfering abutment with said barrel, said means for preventing movement of the housing with respect to the barrel and carrier assembly including a ball carried in a radial slot in the barrel carrier for protrusion therefrom and a circumferentially extending groove in the barrel alignable with said ball protrusion when said barrel is fully seated.

6i. A iluid operated fastener driving tool having a twopiece tool barrel assembly including a barrel removably secured to said tool, a tool housing axially movable relative to said barrel assembly between a safety position at which the tool is inoperative and a ready-to-re operative position for ejecting a fastener through the bore of the barrel into a work surface, said assembly also including means for removably mounting the barrel from the muzzle end of the tool housing, said means comprising a barrel carrier with respect to which the housing is also axially movable between said positions and which has an axial passage therethrough adapted to seat said barrel in normally fixed axially constrained assembled relationship, manually operable and releasable means for normally securing the barrel thus seated in said carrier, and means on said carrier coacting with said barrel and housing for interfering 'with the axial movement of said tool housing to said operative position unless said barrel is fully seated in the carrier, thereby preventing movement of said tool housing to the ready-to-re position, said means being responsive to full seating of said barrel to allow said movement.

7. In an explosive actuated tool for driving a stud, pin, or the like fastener into a work surface, said tool vhaving a barrel including a muzzle, a tool housing longitudinally movable `with respect to said barrel, a breech closure including firing means carried in said housing and a detachable safety shield carrying member with a shield having a work engaging periphery disposed substantially perpendicular to the axis of said tool biased toward said muzzle to cover it with yieldable constraint permitting longitudinal movement of said ,memberV forwardly'I up to and back of said muzzle, latch means in said housing responsive to the absence and presence of said member to respectively prevent and permit full forward movement of said housing, and said housing being mounted on said tool for longitudinal movement of said housing with respect to said shield member and barrel rearward from a normal safety position to a forward ready-to-re position in abutment with said shield member at `which position said shield periphery is in the muzzle plane of the tool and said firing means readied for tiring, the improvement comprising a barrel carrier slidably mounted in said housing for relative axial reciprocating movement between said carrier and said housing, a readily installed and replaceable forwardly extending barrel and mounted in said carrier with axially constraining engagement to form with said carrier a tool barrel assembly and project said barrel from said housing to said muzzle plane which is perpendicular to the axis of the bore of said barrel, axial constraining means means on said barrel for engaging with mating means on said carrier, and means for preventing movement of said housing relative to said barrel and carrier assembly from said normal safety position of the tool to said ready-to-re position of the tool unless said barrel is fully assembled axially at said mating and constraining means Iwith said carrier in said engagement.

8. In an explosive actuated tool for driving a stud, pin or the like fastener from a barrel muzzle axially into a work surface, said tool having a housing, a barrel breech closure and explosive ring means carried in said housing, and a safety shield with a work surface engaging periphery disposed substantially perpendicular to the axis of driving and mounted inwardly of said housing with retention adapted for axial reciprocating movement of said housing with respect to said shield from a rearward normal safety position to a forward ready-to-iire position in abutment with said shield at which position said @ring means is rendered operable and said periphery is in the muzzle plane, also substantially perpendicular to said axis, the improvement comprising a barrel assembly having an outer tubular carrier slidably mounted within said housing for relative axial reciprocating movement between said carrier and housing, and a barrel from a series of interchangeable barrels each of different caliber, said barrel having a reduced breech dimensioned to be rearwardly seated from said plane into said carrier and having a muzzle end in reciprocatable relationship with said shield to project from said carrier and housing to said muzzle plane, axial constraining means on said barrel adapted at said muzzle end to permit manual operation of said constraining means for threadedly engaging and disengaging with mating means on said carrier for keeping said barrel normally secured thereto, and safety means for preventing said movement to said ready-to-re position unless the barrel is fully seated with said constraining and mating means in engagement, said safety means cornprising a ball carried captive in said carrier in a radial aperture therethrough for extending from said aperture, and a circumferential groove in said breech for receiving the inward ball extension only when the barrel is fully seated, said safety means being responsive to absence of full seating by xed outward ball extension interfering with movement to said ready-to-re position.

References Cited in the tile of this patent UNITED STATES PATENTS 2,470,117 Temple May 17, 1949 2,479,431 Temple Aug. 16, I1949 2,494,298 Jones `lan. 10, 1950 2,518,395 Sopris Aug. 8, 1950 2,533,851 Temple Dec. 12, 1950 2,679,645 Erickson June l, 1954 2,918,674 Skumawitz Dec. 29, 1959 2,945,236 Kopf et al July 19, 1960 2,963,707 Schulz Dec. 13, 1960 FOREIGN PATENTS 161,471 Australia Feb. 25, 1955 708,692. Great Britain May 5, 4 717,468 Great Britain Oct, 27, 1954 

